Reptile & Amphibian Forums

I have been talking to a friend of mine who likes working with wood about building a screen topped shell for a sweaterbox (picture one slot of a rack system with a screen top instead of solid top). Before we had hashed out all the details, he went ahead and built it and it looks great. It is made of plywood and sealed with two coats of Minwax oil based polyurethane. I don't know much about sealers and off gassing but all of my reading here has led me to beleive that oil based stuff is bad. My question is this: am I screwed on this one or will this be usable at some point? There is a faint odor and the poly was applied 2 days ago. Thanks for any info.

Rob

This could be a problem, although with the screen-top design it might be okay.

Questions:

How much of the wood overlaps the inside of the tub?

Did he thin the coats and wipe them on or just apply it straight?

If it were me I'd at least sand off the poly that is exposed directly to the inside of the rubbermaid and use something else to seal it. What that would be would depend on the species.

Or I might just let it offgas for a few months and then cover it with some sort of film or plastic.
-----
Current snakes:

0.0.1 Gonyosoma oxycephala - Java locale (green)

1.2 Gonyosoma oxycephala - Jave local (green)

2.2 Gonyosoma janseni - Seleyar locale (all black)

1.2 Gonyosoma janseni - Celebes locale (Black & Tan)

Hi Chris,

Thanks for the response.

>>This could be a problem, although with the screen-top design it might be okay.

I was afraid you might say that.

>>Questions:
>>
>>How much of the wood overlaps the inside of the tub?

The wood overlaps the tub by about 2.5" on all sides. The opening is 12' x 18" and the tub is the standard rubbermaid sweaterbox that measures 14.5" x 20.5" at the inside top edge.

>>Did he thin the coats and wipe them on or just apply it straight?

I don't know for sure but could find out if that is a big deal.

>>If it were me I'd at least sand off the poly that is exposed directly to the inside of the rubbermaid and use something else to seal it. What that would be would depend on the species.

If I were to do that, what would you suggest. Currently I keep Kenyan sand boas exclusively but it would be reasonable to expect smooth scaled sand boas or corn snakes as well.

>>Or I might just let it offgas for a few months and then cover it with some sort of film or plastic.

Probably will start with the long offgas period as I am not in dire need to put it to use. After the offgas period, what sort of film or plastic would you suggest? Also, would it be better to let it offgas in my garage/unfinished portion of my basement/under my carport or does it not really matter?

Thanks again for all of your help.

Rob
>>-----
>>Current snakes:
>>
>>0.0.1 Gonyosoma oxycephala - Java locale (green)
>>
>>1.2 Gonyosoma oxycephala - Jave local (green)
>>
>>2.2 Gonyosoma janseni - Seleyar locale (all black)
>>
>>1.2 Gonyosoma janseni - Celebes locale (Black & Tan)

At this point the polyurethane is in the second stage of its curing process so temperature and humidity are not so important, or so I've been told. Still, I'd be inclined to let them sit in a warm/dry area if possible.

If you do let them cure you could then seal with graphic vinyl film or shelf liner.

If you sand it off I would probably just buy a spray can of water based poly and spray on several thin coats. Unless you need extra for another project, then I'd buy a can and brush it on. Since this is the lid of the cage very little protection is needed.

Either way, make sure that you are buying water based but especially if you go with a spray on poly. Last I checked very few spray can polys were water based.
-----
Current snakes:

0.0.1 Gonyosoma oxycephala - Java locale (green)

1.2 Gonyosoma oxycephala - Jave local (green)

2.2 Gonyosoma janseni - Seleyar locale (all black)

1.2 Gonyosoma janseni - Celebes locale (Black & Tan)

Thanks for all of you help Chris, I appreciate it as always. I will probably just let it continue to cure for a while and then put the vinyl film on it. I would really rather avoid getting into sanding and reapplying.

One last thing, and this is probably a really stupid question but, what is it about the oil based products that make them so bad?

Thanks again for your time.

Rob

Oil-based finishes cure in two stages. First is the solvents flash off leaving a hardened skin on the surface. Once these solvents have flashed off a exothermic reaction takes over which relys on oxygen. This oxygen is inhibited by the surface film that forms when the solvents flash off. Due to this the solvents in the middle of the film layer are somewhat trapped and take a long time to offgas.

With modern VOC restrictions companies have been forced to reduce the amount of solvents in their products. What happens is that the average user ends up appying these products too thick and the problems described above are made even worse.

I do believe that oil based products could still be used in a reptile cage but only if they were applied in a way very different than recommended.

Typically the finishing schedule or urethane means that subsequent coats are applied during a tight window where the previous coat is somewhat cured but still at a point where the next coat can burn in. I think you can see how this would really affect the problems I have already described. Not only is the original surface film impeding the curing process, but now the second, third, etc, coats are impeding that even further.

What I would do is to thin down the urethane with a solvent and wipe it on as thin as possible. And instead of applying the next coat during that tight window of opportunity, I would wait for the coat to fully cure and then apply the next coat. You'd have to scuff sand inbetween coats to allow the next coat to adhere since they could no longer burn or melt into each other.

Obviously this would add an extraordinary amount of time it takes to finish a cage as not only would more coats be required, but a coat could only be applied every couple of weeks, maybe less, maybe more.

But given how long some people wait for cages to offgas, this might not be such a bad thing.

Oil-based urethanes offer an incredible amount of protection for the money. They are cheap and readily available. But even in the hands of the experienced you can end up with a very thick coat with an interior that is basically still soft. Many a talented woodworker has had to spend hours sanding off very gummy urethane in order to salvage an expensive project.

-----
Current snakes:

0.0.1 Gonyosoma oxycephala - Java locale (green)

1.2 Gonyosoma oxycephala - Jave local (green)

2.2 Gonyosoma janseni - Seleyar locale (all black)

1.2 Gonyosoma janseni - Celebes locale (Black & Tan)

.

Great info in this thread.

I made lots of box tops much like you've described over the years, and had the same issues. The oil-based products are very durable but offgas for months. When you put the lid on the plastic box, you will really smell the odor in the box after some time.

Fortunately your box top is well-ventilated, so you may get away with a shorter wait time.

Anyway, I learned a few things along the way.

For flat parts of the lid (like the 2.5" rim over the box) you can use adhesive contact paper. The stuff works really well and is easily replaceable when needed. You may need to nail or screw (small nails or screws) some small molding to hold the edges of the contact paper down depending on humidity in the box. You may need or want to paint the wood before applying the contact paper. I just use enough water-based paint to give the wood surface a smoother feel. Usually just one coat and then a good sanding.

For exposed edges of wood, like the cut edge of plywood, I just spread on a very thin coat of wood glue, let it dry, give it a light sanding, then apply a thin coat of water-based paint. That is it. Easy.

What I've described is generally durable enough for the job. And easily tweakable if needed. I mean, you can ditch the contact paper at any time for something else if you want. I find contact paper durable enough for general usage and so darn easy to replace.

Good luck.
-----
Mark

.